Watch: Christchurch mother Libby McKenzie's miracle baby

After years of trying, and three heart-wrenching rounds of in vitro fertilisation, 36-year-old Libby McKenzie hugs the beautiful baby boy she always dreamed of.

Two-month-old Mac is the first baby born in New Zealand through a genetic screening technology process available here for the first time.

Pre-implantation Genetic Screening (PGS) is used to examine embryos created during routine IVF treatment, enabling only those which have the correct number of chromosomes to be selected.

Having only embryos with the right number of chromosomes reduces the chance of miscarriage, and greatly increases the chance of a healthy baby.

Christchurch HR executive McKenzie and her husband had already gone through the stress, heartache and expense of two rounds of IVF when they heard of PGS.

Fertility Associates told the couple that the clinic had signed up with Canterbury Health Laboratories to offer the service in New Zealand for the first time.

It added another $3100 to the already costly IVF process, but the extra information, and clarity around why they had so far been unsuccessful, was worth the money, they believed.

During the McKenzies' third round of IVF, they had three embryos.

One was not tested, another was ruled out due to chromosome issues, and the third one was identified as a "viable embryo".

It was put back and months later would result in the healthy, happy baby Mac.

"We knew that this one should work, and it did. Baby Mac came along and made it all worthwhile," McKenzie said.

"He's just so cool and it's just an amazing experience being a mum."

PGS was introduced to New Zealand last year.

Now, about 15 per cent of clients going through IVF treatment with Fertility Associates are also choosing PGS.

Dr Mary Birdsall, chairwoman of Fertility Associates and fertility specialist, expects that number to steadily rise.

"In the US it's well over 50 per cent," she said. "The trend is that people like this technology."

Fertility Associates says PGS particularly benefits women aged 36 and over, women who have had recurrent miscarriages, and women who have not become pregnant despite the transfer of several embryos.

Data shows PGS can result in birth rates as high as 65-70 per cent for normal embryos while offering a lower miscarriage rate.

It also gives people more certainty around the likely outcome of treatment.

"We're excited to be able to offer PGS in New Zealand, because while we have been able to do this technology for quite some time, we used to have to courier the cells to either an Australian or American lab which would [double or triple the costs]," Birdsall said.

"It's become a little bit more likely to be affordable now that we can offer this in New Zealand."

How it works

• Pre-implantation Genetic Screening offers couples a way of selecting which embryos have a better chance of progressing to become a healthy baby by identifying those that have the right number of chromosomes.

• In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. Extra or missing chromosomal material can cause problems in foetuses.

• About 5-6 cells are biopsed from each blastocyst into a fine glass needle

• The blastocysts are frozen for later use

• The cells are sent to a specialist genetic laboratory for analysis

• Chromosinally normal blastocysts are transferred at a later date after thawing

• Birth-rates can be as high as 65-70 per cent for normal embryos

• There is also a lower miscarriage rate

• Women aged 36 and over, or those who have had recurrent miscarriages, are most likely to benefit